HK1078728B

HK1078728B - Transducer motor/generator assembly

Info

Publication number: HK1078728B
Application number: HK05110359.9A
Authority: HK
Inventors: 罗兰．P．特兰达菲尔
Original assignee: 罗兰．P．特兰达菲尔
Priority date: 2002-02-05
Filing date: 2003-02-05
Publication date: 2011-04-15

Description

Converter type motor/generator assembly

Technical Field

The invention relates to an electrically and magnetically operated switch, a magnet and an electromagnet; more particularly, the present invention relates to a magneto-mechanical power device having relatively movable coils and permanent magnet assemblies.

Background

Various converter assemblies are known. One type is shown in figure 1 as shown in U.S. patent No. 5,142,260 to William n. The assembly includes a magnetic circuit structure 10 with two aligned magnetic disks 12, 14 that are polarized and oriented in an axial direction so that the magnetic flux fields they form oppose each other. A spacer 16 of ferrous or non-ferrous material is interposed between the magnets 12, 14 to assist in controlling the magnetic field characteristics. As a result of the opposite axial alignment, the magnetic flux lines 18 emanating from the poles 20, 22 face each other and are focused and radiate outward from the region 24 between the magnets 12, 14.

This prior art structure serves two functions, namely increasing the number of flux lines per unit cross-sectional area of the region adjacent the structure's outer surface 26; and directing the flux lines 18 in a path substantially perpendicular to the structure axis 28. Ideally all of the flux lines 18 emanating from the structure 10 are oriented perpendicular to the structure axis 28 to achieve maximum force on the columnar conductors 30 for their axial length. But as described in the' 260 patent, the flux line regions are non-perpendicular to the structure axis. If current carrying conductor 30 is moved in an axial direction from center region a to magnet center region C, the instantaneous force on conductor 30 decreases as a function of angle to zero in a direction parallel to axis 28. The result is the "field commutation" described in the' 260 patent. "field commutation" is typically one of the limitations encountered by closed loop path structures such as the structure 10 of FIG. 1. Such that movement of the coil 30 in a linear direction generally occurs only within a relatively short portion of the axial length.

These problems are addressed in U.S. patent No. 5,142,260, which is the inclusion of one or more additional radial magnets and/or spacers between opposing magnets of a prior art magnet assembly. The outer pole of the radial magnet has the same polarity as the facing pole of the magnet. The flux lines emanating from the radial magnets oppose the axial magnet field and are directed outwardly to a path perpendicular to the structure axis. The flux lines of the radial magnet travel outward and wrap around to opposite magnetic poles of the axial magnet. This increases the total flux lines provided by the structure, as described by the' 260 inventor.

There are several disadvantages associated with the device described in U.S. patent No. 5,142,260. It is apparent that the' 260 inventor sought to improve coil performance by increasing the coil field interaction distance and by ensuring that the drive coil wires are as close as possible to the magnet assembly. Thus, both the coil and the outward magnetic field flux lines are lengthened. This step results in an increase in the weight and complexity of the magnetic system and further in an increase in the coil force, resulting in a non-linear response of the coil to the magnetic field as the coil oscillates during excursion. Such systems are generally inefficient in that they require many windings to allow their drive column to effectively interact with the increased field size. In addition, overheating and/or cooling may be easily caused, and various signal distortions may develop during use. Summarizing, the foregoing problems result in' 260 devices that are inefficient, bulky, and expensive to manufacture. In addition, there is a long term zero or counter force on the coil during pole commutation.

To address several of the aforementioned shortcomings, designers have attempted to constrain excursion distance and design relatively flat converters. For example, U.S. patent No. 5,668,886 to Sakamoto et al describes a loudspeaker having two magnets with like poles facing each other held in place by opposed frame members. The iron-containing core plate is inserted between the two magnets. The columnar voice coil is positioned and sleeved on the magnet and the core plate. The diaphragm is mounted to surround the outer periphery of the voice coil. The' 886 device is apparently similar to a dynamic transducer, but uses a ferrous core plate to direct a single radially emanating magnetic field outward. The' 886 device is still relatively heavy and requires a tall, cylindrical drive coil to interact with the magnetic field at close range.

The device of U.S. patent No. 5,764,784 to Sato et al describes a single disc magnet secured to the inner surface of a flat housing. A diaphragm is disposed within the housing and is spaced from the magnet. A relatively short hollow cylindrical drive coil is coaxial with the magnet and is secured to the opposite face of the diaphragm. According to' 784, the inventors have this configuration to reduce power consumption, reduce thickness, and improve efficiency. However, a disadvantage of the' 784 device is that the diaphragm is limited in the distance traveled during use because if the input signal is strong enough, the diaphragm quickly hits the magnet face. Furthermore, the' 784 drive coil is fully immersed in the symmetric magnetic field during its excursion travel. This affects signal purity and may constitute a source of signal distortion.

U.S. patent No. 5,905,805 to Hansen describes a transducer with a circular center diaphragm. A flat planar drive coil is formed on one surface of the diaphragm, with a pair of opposed cylindrical magnets disposed, one spaced from each side of the diaphragm. The magnets are in a mutually exclusive configuration with like poles facing each other. This produces a radially emanating magnetic field. However, like the '784 device, the' 805 device is also limited in the distance the diaphragm can travel before it hits one of the cylindrical magnets. This design also has the problem of a relatively small amount of interaction between the planar coil windings and the radially emanating magnetic field.

There is thus a need for a converter which avoids the aforementioned disadvantages. Ideally, such converters should also be light, thin and small. The drive coil interacts efficiently with the magnetic field, producing higher linearity of response over a larger spectral range. In addition, the improved converter does not overheat or require cooling, thus maintaining a high and more consistent power output during operation. Similarly, the power output available per unit weight of the device is greater and the coil has a greater excursion distance.

Disclosure of Invention

The present invention is directed to satisfying these and other needs as discussed herein. An electromagnetic transducer is described having a magnet assembly and an inductive drive coil. The magnet assembly includes first and second opposing outer pole faces and a radially outwardly emanating magnetic field. The inductive drive coil is a flat ring coil shaped to have a width greater than or equal to a height. The drive coil is located in the radially emanating magnetic field of the magnet assembly. A space exists between the magnet assembly and the drive coil so that during use, the drive coil is not in physical contact with the magnet assembly. The drive coil moves along an excursion path, wherein at least a portion of the excursion path is located between the outer pole faces of the magnet assembly. When assembled, the drive coil is mounted adjacent the magnet assembly so as to be axially movable relative thereto in use. When used as a motor, current is supplied to the coil, causing the coil and magnet to move relative to each other. When used as a generator, the external physical movement of the drive coil relative to the magnet causes the drive coil to generate a corresponding current.

According to other aspects of the invention, the magnet assembly may be shaped to be magnetized either axially or radially. In addition, a single magnet may be used or multiple magnets may be arranged with like poles facing each other. In one embodiment, the magnet assembly is formed from a pair of axial disc magnets. The disc magnet includes a diameter dimension. The drive coil has an inner diameter that is greater than the diameter of the disc magnet so that the drive coil surrounds the disc magnet. In another embodiment, the magnet assembly includes two axial ring magnets. The ring magnet forms an outwardly radiating magnetic field and an inwardly radiating magnetic field. The drive coil is annular and can be positioned in either of two magnetic fields.

Various magnet assembly shapes may be used in accordance with other aspects of the invention, such as arcuate magnets or rectangular magnets.

According to yet other aspects, various speaker devices and microphone devices are described, each made in accordance with the present invention.

Drawings

The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 shows a side view of a prior art permanent magnet motor assembly;

FIG. 2 is a side view of a first embodiment of a permanent magnet motor assembly constructed in accordance with the present invention;

figure 3 is a perspective view of a first embodiment of a drive coil made in accordance with the present invention;

FIG. 4 is a cross-sectional side view of the coil of FIG. 3;

figure 5 is a perspective view of a second embodiment of a drive coil made in accordance with the present invention;

FIG. 6 is a cross-sectional side view of the coil of FIG. 5;

figure 7 is a perspective view of a third embodiment of a drive coil made in accordance with the present invention;

FIG. 8 is a cross-sectional side view of the coil of FIG. 7;

figure 9 is a perspective view of a fourth embodiment of a drive coil made in accordance with the present invention;

fig. 10 is a cross-sectional side view of the coil of fig. 9;

figure 11 is a perspective view of a fifth embodiment of a drive coil made in accordance with the present invention;

fig. 12 is a cross-sectional side view of the coil of fig. 11;

figure 13 is a perspective view of a sixth embodiment of a drive coil made in accordance with the present invention;

fig. 14 is a cross-sectional side view of the coil of fig. 13;

FIG. 15 is a cross-sectional side view of another embodiment of a transducer made in accordance with the present invention, showing an interface member;

FIGS. 16, 17 and 18 are cross-sectional schematic side views of other alternative embodiments of transducers made in accordance with the present invention, illustrating the use of spacers, end caps, and spaced apart magnet arrangements;

FIGS. 19, 20, 21 and 22 are cross-sectional schematic side views of yet another alternative embodiment of a transducer made in accordance with the present invention, illustrating the use of a ring magnet;

FIGS. 23, 24, 25 and 26 are cross-sectional schematic side views of yet other alternative embodiments of a transducer made in accordance with the present invention, illustrating the use of single magnet and multiple magnet arrangements;

FIGS. 27, 28, 29, 30, 31, 32 and 33 are cross-sectional schematic side views of still other alternative embodiments of a transducer made in accordance with the present invention, showing various ring magnet configurations;

FIGS. 34, 35 and 36 are cross-sectional schematic side views of other alternative embodiments of transducers made in accordance with the present invention, shown with concentric ring and/or disc magnet arrangements;

FIGS. 37, 38, 39, 40, 41, 42, 43 and 44 are cross-sectional schematic side views of other alternative embodiments of a transducer made in accordance with the present invention, shown with a non-circular magnet configuration;

FIG. 45 is a schematic perspective view of an example support device formed in accordance with the present invention;

figure 46 is a schematic side view of an embodiment of a speaker formed in accordance with the present invention;

FIGS. 47, 48 and 49 are schematic perspective views of exemplary surroundings formed in accordance with the present invention;

FIGS. 50 and 51 are schematic side views of another speaker embodiment made in accordance with the present invention and having a movable magnet assembly;

FIG. 52 is a schematic plan view of an example loudspeaker showing an embodiment of a support body;

FIG. 53 is a schematic side view of two speaker assemblies each incorporating the speaker of the present invention in place of the prior magnet system and bar chart;

FIG. 54 is a schematic side view of a motor/generator arrangement with dual transducers and diaphragms;

FIGS. 55, 56 and 57 are schematic side views of a microphone made in accordance with the present invention, each having a fixed magnet assembly and a movable diaphragm;

FIG. 58 is a schematic side view of a microphone made in accordance with the present invention and having a movable magnet assembly;

FIGS. 59, 60 and 61 are schematic side views of various monopole embodiments of microphones made in accordance with the present invention;

FIGS. 62, 63 and 64 are schematic plan views of examples of the support; and

fig. 65 and 66 are schematic side views of two speaker/microphone embodiments made in accordance with the present invention.

Detailed Description

The present invention relates to converter motor and/or generator assemblies, and more particularly to a non-return converter assembly configuration. The invention is useful for a variety of applications in the very low to ultrasonic and radio frequency spectrum, including acoustic devices, relays, switches, oscillators and other energy conversion devices, as sensors and signal transmitters.

Referring now generally to fig. 2, a permanent magnet assembly 50 is provided for reciprocating a current carrying conductor 52 formed in a horizontal plane 54. The magnet assembly provides a magnetic field that extends outwardly and transverse to the vertical or axial magnet direction (the directions provided in this description refer only to the drawings. The conductor 52 is separated from the outer surface 56 of the assembly 50 by various means, such as an intermediate surface material and/or a surrounding support structure. In accordance with the present invention, the conductive drive coil has an overall height that is less than or equal to its overall radial width defined by the difference between the inner and outer dimensions of the coil. Such coils are generally referred to herein as flat ring coils.

Alternating current flowing through conductor 52 causes conductor 52 to reciprocate in the direction of arrow 62 generally in the axial direction of magnet assembly 50. If other elements are attached to the drive coil, these other elements may also reciprocate together. When so configured, the converter is referred to herein generally as a motor. Alternatively, the transducer may be used as a generator, in which case movement is converted into an electrical signal by movement of the coil relative to the magnet assembly. If the transducer is used as a generator, the external mechanical oscillations cause the coil to move within the magnetic field provided by the magnet assembly. This movement generates a corresponding current in the coil.

Still in further detail with reference to the embodiment of fig. 2, the outwardly emanating magnetic field is generated by positioning two magnets with like poles facing each other (i.e., in either a south-south or north-north arrangement). The magnet assembly of fig. 2 includes first and second permanent disc magnets 64, 66, each magnetized in an axial direction. The axis of the magnet assembly of figure 2 is indicated at 72. By positioning the same poles face to face, the flux lines radiate outwardly from the opposing faces of the first and second magnets in a radial direction, i.e., in a direction parallel to the pole faces and transverse to their axial magnetization direction. The first and second magnets generate magnetic flux lines that emanate outwardly in a radial direction from the first and second magnets and return to their opposite poles. In fig. 2, the first and second disc magnets are positioned directly face-to-face with each other and are of equal diameter at the location of the outwardly emanating magnetic field.

Various coil arrangements are possible, several examples of which are illustrated in fig. 3-14. Typically, the drive coil has a circular shape with a height H and a width W. The height of a coil is defined as the distance between the upper surface and the lower surface of the winding of the coil. The coil width is defined as the distance between the inner and outer horizontal dimensions of the coil. For example, using a circular drive coil, the width is defined as the radial spacing between the inner and outer diameters of the coil. According to the teachings of the present invention, the coil width is at least equal to the coil height. For this reason, the coil of the present invention is generally defined as a flat ring coil.

The drive coil is preferably a flat ring that is helically wound about its inner diameter. In the embodiment of fig. 3 and 4, the windings have a circular cross-section. The cross-sectional shape is rectangular in fig. 5 and 6. The embodiment of figures 7 and 8 shows the drive coil being comprised of a single layer of upstanding ribbon wire windings. In fig. 9 and 10, the drive coil is comprised of a single layer of straight flat wire single layer windings. In fig. 7-10, the wire spacing is exaggerated for illustration. In multiple applications, the windings can be more compact. FIGS. 11 and 12 show a single turn of the wire. FIGS. 13 and 14 show multiple turns of a transverse wire. In some embodiments, the drive coil may be formed from multiple layers of windings (see fig. 5 and 6).

Referring back to fig. 9 and 10, the drive coil is a rectangular flat wire that is spirally wound in an upright orientation. The inventors have now appreciated that the use of flat or ribbon wire instead of round wire as the coil improves switching performance because the field strength decreases with increasing distance from the source of the field. Flat or ribbon wire is more suitable for use as the drive coil, and more turns of wire may be more closely stacked to the magnet source. The wire is wound with its broadside oriented vertically where the wire height is parallel to the longitudinal axis of the device (like a roll of tape). Excellent experimental results were obtained using a flat wire cross-sectional ratio of 3: 1 (height: width), with the wire height in the vertical axis, the greater the possible number of flux lines, and the ability to traverse the coil windings when immersed in a radial magnetic field. In some cases, depending on the particular application, a 4: 1 or even 8: 1 wire cross-sectional ratio may provide advantages. Sense lines with a large height-to-width ratio (i.e., five or more than one) may be referred to generally as striplines.

The coil may also be made of a wire made of an inductive alloy coated on a thin dielectric material, such as plastic. In some cases, the wires may be in a planar arrangement (i.e., formed directly on the membrane or other support member), in which case the wide sides of the wires are horizontal. This arrangement is less effective for certain applications than the vertical ribbon winding of flat wire.

In each case, the overall coil height approaches its radial width, but does not exceed the radial width. In a preferred embodiment, the coil has a plurality of windings, and the width of the coil is substantially greater than the height. The drive coil may be made of different types of wires in terms of shape and material composition. The choice of materials is largely determined by the performance characteristics desired for a particular application of the transducer. The choice of conductor is also influenced by factors such as output power, frequency range, and physical size of the device.

When designing a transducer for a particular application, the total coil height must not be too large, otherwise the coil portions will not interact efficiently with the magnetic field, which may result in an unnecessarily heavy and thick transducer.

After assembly, the drive coil is positioned outside the magnet, thereby causing the coil to be positioned in an outwardly emanating magnetic field where the coil's interaction with the magnetic field is optimized. The drive coil is concentric with the magnet, and the coil axis is shared with the magnet axis. The coil body is in a horizontal plane perpendicular to the longitudinal axis of the element. The coil transversely divides the first and second magnetic regions, with the coil being in a substantially horizontal plane of symmetry. The magnet assembly is therefore bilaterally symmetrical across the horizontal plane. Half of the magnets can be seen as mirror images of each other with the coils in the mirror position, or at the level of themselves. (from a mathematical point of view, the horizontal plane of symmetry has only a radial magnetic field vector component and no axial component.

In a divergent radial magnetic field where the magnetic field spreads outwardly from the outer surface of the disc magnet, the drive coil has an inner diameter that is slightly larger than the outer diameters of the first and second disc coils. As shown in fig. 2, there is a narrow space s between the drive coil and the magnet. Such space s is preferably as small as possible without causing the drive coil to contact the magnets during use. For example, in one embodiment, the spacing s is in the range of about 0.5 mm to about 5.0 mm. It is to be understood that the size of the space is preferably proportional to the size of the magnet. The larger the magnet, the larger the magnetic field generated and the larger the allowable space size. The coil and magnet non-contact position allows the coil to move freely up and down the periphery of the magnet assembly within a desired coil excursion distance. So that the drive coil is not directly physically obstructed by the magnets. The coil is close to the magnet and the coil is maintained in close relation to the magnetic field where the magnetic field density is strongest. Typically the size of the space s, the type of drive coil configuration, and the type of material used will depend on the predetermined magnetic field strength, the desired input, and the desired transducer performance.

When used as a motor, current is supplied to the coil causing the coil to move relative to the magnet assembly. In addition, if the transducer is used as a generator, external oscillations cause the coil to move within the magnetic field provided by the magnet assembly. This movement correspondingly generates a current in the coil.

Numerous variations can be made using the basic invention description hereinbefore, each as described in detail hereinafter. One variation is to use a flexible interface member between the magnet assembly and the drive coil. The interface member may assist in the manufacture of the transducer. It may also be used to alter the response of the drive coils and/or limit the excursion distance of the coils. Another variation uses spacers, end caps, radial magnets and multiple discs to assist in shaping the outward-radiating magnetic field shape of the magnet assembly. Yet another variation is to form a magnet assembly with only a single magnet. Alternatively, the magnet assembly may be made using more than two magnets.

An optional flexible interface member 80 may be used in such a space depending on the magnet assembly configuration and the particular performance characteristics desired. In the embodiment shown in fig. 15, the interface member is located between the first and second magnets and is directly adhered to the facing surfaces of the magnets. Thus, the interface member is located at the device level, the top surface of the interface member is glued to the top magnet bottom surface, and the interface member bottom surface is glued to the bottom magnet top surface. (alternatively and depending on the configuration, rather than being attached to a disc-shaped magnet, the interface element may be attached to a spacer, a radial magnet, a ring magnet, or several other shaped magnets in a magnet pair or a single magnet.

The attachment of the interface member to the drive coil preferably does not impede coil oscillation, but is sufficiently robust to dampen coil movement near excursion limits, if desired. Fig. 15, the interface member is circular with its outer periphery bonded to the inner periphery of the drive coil. Any known attachment method is contemplated, including bonding, adhering, and the like. Alternatively, the drive coil may be attached to the upper or lower surface of the interface member. The drive coil may be attached to the upper and lower surfaces of the interface member when the drive coil has multiple stacked windings.

Movement of the drive coil relative to the magnet occurs along a path referred to as the "excursion path", denoted herein as "e". The coil excursion path is the vertical distance traveled by the coil relative to the magnet assembly during operation. As described above, the interface member can be used to alter coil movement within the coil excursion path and/or dampen coil movement at the limits of the coil excursion path. The interface size and materials are determined based on the type of drive coil used, the strength of the magnetic field, the expected input, and the desired transducer performance.

The inventors have appreciated that the choice of interface material is based primarily on the device frequency range and the desired damping properties. For example, at low frequencies, no interface member is required (see FIGS. 2 and 18) or only a very flexible thin material is used. In this way the material does not over-damp the large excursion path required. For the case of successively higher frequencies, thinner and stiffer materials are suitable choices for interfacing these components. As the frequency increases, the excursion path length decreases proportionally. Typically the magnitude of the excursion distance will vary depending on the input frequency. The frequency is small, resulting in a proportional reduction in excursion distance.

Shaping of the outwardly emanating magnetic field may be accomplished using spacers, end caps, and radial magnets. Referring to fig. 16, an annular ferrous spacer 90 is disposed between the first and second disc magnets. In fig. 17, circular ferrous end caps 92, 92' are used above and below the first and second magnets to shape the magnetic return path. In one embodiment, the spacer, end cap and disc magnet are of equal diameter. Alternatively, the spacers and end caps may be made of a non-ferrous material (e.g., a dielectric material, i.e., wood, bone, plastic, etc., or a conductive material, i.e., iron, zinc, aluminum, silver, etc., or an alloy combination of all or a portion of these materials), or the spacers or end caps may be of varying sizes. Such spacers and/or end caps may take on numerous shapes such as discs, rings, rods, etc. The ferrous spacer and end cap may be of equal, smaller or larger size relative to the magnet or relative to each other. The non-ferrous spacer and end caps are preferably smaller or equal in size (smaller or equal in diameter or other relevant width dimension) than the magnet itself. For example, when disc magnets are used, the spacer and end caps have a diameter less than the disc magnet diameter. In general, the particular dimensions and materials will depend on the flux line shape desired for a given application.

Fig. 18 does not use an interface member, spacer or end cap. Instead, the first and second magnets are positioned spaced apart from each other, thereby forming an open space therebetween. This also has an effect on the shape of the outwardly radiating radial magnetic field. (this spaced relationship is similar to element 170 shown in FIG. 45 and can be achieved using a second structural member).

Referring to fig. 19, a radially magnetized permanent ring magnet 100 has a radially inner magnetic pole of opposite polarity to the opposite magnetic poles of the first and second magnets and a radially outer magnetic pole of the same polarity as the opposite magnetic poles. This arrangement shapes the magnetic field of the magnet assembly to have a more uniform radial magnetic field over a higher percentage of the total length of the assembly. In radial magnets, the magnetic field emanates from the sides or periphery of the ring structure, so that the curved outer and inner faces are effectively pole faces. The flat ring coil is nested at a mid-height of the single ring radial magnet, or inside the inner diameter of the magnet. If more than one ring magnet is used in the magnet assembly, the drive coil is centered in the horizontal plane that achieves the maximum flux density. The spacers 94 or gaseous openings may be disposed between the magnetic poles and the radial magnets (see fig. 20 and 21) or between a plurality of radial magnets (see fig. 22).

In yet another embodiment, the magnet assembly is formed with only a single magnet. Refer to fig. 23. The single magnet assembly is particularly useful for higher frequency applications where a smaller excursion distance dimension is desired. However, in axial magnet systems, the flat ring coil position is not at the center height of the magnet. While this arrangement is correct for establishing physical symmetry (bilateral across the horizontal plane), the magnetic field lines across the coil are incorrect. In this position, the coil is not exposed to the radially emanating magnetic field and is therefore not in its weakest interaction position with the associated magnet. The drive coil of the present invention is most effective when placed in a magnetic field region having a radial magnetic vector that is greater than an axial magnetic vector. When the axial magnetic component is greater than the radial magnetic component, the coil performance is diminished. Thus, in a single magnet axial assembly, the drive coil is positioned in the region of the magnet pole face, which is located approximately at the midpoint of the excursion range. For efficient operation, the drive coil may be in a convergent or divergent magnetic field design, free to move around the magnet assembly above and below the pole face. This maintains the coil within the region of strongest radial flux density.

For a single magnet, the radiation source comes from the fringe fields near (magnetized in an axial orientation) the magnet faces and magnet side corners. This radiation region occurs in a narrow region, slightly above or below the magnet surface, near the corner of the magnet where the magnetic field is strongest. The flux lines radiate outwardly parallel to the pole face surface. This radial radiation is most effective for the performance of the flat ring coil. The reason is that the maximum density of flux lines is slightly above or below the pole face, which becomes important for the coil to be free to oscillate in this region.

In a single axis magnet system, the drive coil is preferably positioned close enough to the outer surface of the magnet so that the magnetic field emanating from the magnet pole face radiates laterally outward at the pole face and generally radiates at symmetrical angles above and below the pole face. In a single axial magnet configuration, the strongest interaction location of the drive coils is flush with the magnet pole faces to achieve the maximum radial magnetic field through the flat drive coils. In addition, the drive coil width need not extend too far from the magnet assembly, since the radially emanating magnetic field above and below the plane of the pole surface becomes more and more asymmetric as the radial distance from the magnet increases. In the more distant regions, the magnetic field also becomes weaker and less suitable for use. In other words, the magnetic field strength and symmetry decrease with distance from the magnetic field. Closer to the magnetic field, these properties increase. Thus, when determining the size and number of windings of the drive coil, consideration must be given to the magnetic field strength and horizontal symmetry about the pole face.

For a single radial ring magnet, referring to fig. 32, the horizontal plane would intersect horizontally across the center height of the ring. This location is the magnetic symmetry plane where the radial magnetic field strength is at a maximum. If several radial ring magnets are stacked on top of each other, the horizontal symmetry plane is located in the center of the area with the greatest magnetic flux density. This positioning creates a similar magnetic field pattern above and below the plane. Bilateral field symmetry is an important factor in the formation of a sharp signal.

As shown in fig. 24, various end caps may be used to further create the outwardly emanating magnetic field. Figure 24 also shows the flat drive coil 52' being attached to the first flat drive coil 52 by a form 108. In addition, the second drive coil 52' may not be coupled to the first drive coil, e.g., to achieve a different frequency.

Fig. 25 and 26 illustrate an arrangement in which the magnet assembly includes a plurality of magnets arranged one above the other in a stacked arrangement. The magnets are arranged with like poles facing each other. The drive coils may be used for each radially emanating magnetic field. An optional former 108 joins the coils to provide the engagement movement. The magnet assemblies also form a magnet assembly whose magnetization has both radial and axial directionality (see fig. 22). Additionally, the magnet assembly may include only radially oriented magnets, or only axially oriented magnets.

The foregoing embodiments describe drive coils that sheath radially divergent magnetic fields (i.e., circularly outwardly emanating). The second main embodiment includes a drive coil positioned within a radially convergent magnetic field (i.e., moving inward in a radial direction). Referring to fig. 27, the magnet assembly includes first and second ring magnets that are permanently magnetized in the axial direction. In this embodiment, the ring magnets are stacked flush on top of each other with like poles facing each other. Forming a divergent radial magnetic field by taking the outer diameter of the annular magnet as the center; and forming a convergent radial magnetic field centered on the inner diameter of the ring magnet. The drive coil may be located in one or the other of the emanating magnetic fields.

The coil wire cross-section encompasses any of the various geometries described herein, and the cross-sectional shapes need not be similar when there is more than one drive coil. In a convergent magnetic field, the drive coil outer diameter is slightly smaller than the ring magnet inner diameter so that the coil is free to move along a vertical excursion path within the ring magnet. In the divergent magnetic field, the inner diameter of the drive coil is larger than the outer diameter of the ring magnet. The drive coil remains close to the magnet but does not contact the magnet or physically collide with the magnet. Since the magnetic field is strongest just outside the inner and outer edges of the toroid, the coil is preferably placed as close to the magnet as possible to take advantage of the maximum available flux density.

Fig. 28-33 show another embodiment similar to that described above with respect to the disc magnet. Multiple or single ring magnets (radial or axial magnetization), inner and outer drive coils, flexible interface members, spacers, open spacers, end caps, axial disc magnets, and shaped pieces may also be used in various combinations to form a magnetic field having a particular shape and a particular strength. Fig. 27-33 show only some of the possible arrangements. In fig. 32, the drive coil is positioned relative to a single radial ring magnet at the mid-height of the magnet, which is the horizontal plane where the magnetic flux density is greatest, providing maximum magnetic field symmetry around this plane.

Referring to fig. 34, 35 and 36, a plurality of toroids may be used to form a plurality of diverging and/or converging radially emanating magnetic fields. Magnet pairs of different sizes and magnetic field strengths may also be provided. Various arrangements include magnet assemblies comprising concentric magnets or magnet pairs. Fig. 34, the magnet assembly uses pairs of axial disc magnets 64, 66 located inside pairs of axial ring magnets 64 ', 66'. The disc magnet and the ring magnet are positioned with like poles facing each other but with opposite polarities (i.e., the disc magnet south poles facing each other and the ring magnet north poles facing each other and vice versa). A total of three drive coils are provided as shown. A coil 52 surrounds the outer diameter of the disc magnet assembly. Another coil 52 'is located at the inner diameter of the ring magnet assembly and finally, a third coil 52' is located at the outer diameter of the ring magnet assembly. As shown in fig. 35 and 36, radial ring magnets replace one or more pairs of concentric magnets.

In the non-concentric embodiment described above (e.g., with reference to fig. 2), the drive coil is immersed in an open field because the magnetic circuit fails to complete the circuit itself through the outer periphery of the coil. In other words, the flat ring coil is immersed in a magnetic monopole source of one or more magnets. There is a single boundary between the coil and the magnet. The outer periphery of the coil is not bounded. If the magnetic circuit is closed, this region is called the dipole gap. The dipole gap represents a closed field. In the closed field, the inner and outer diameters of the coil are bounded by the proximal end of the magnet surface.

For embodiments having concentric magnets or magnet pairs, the magnetic field formed between the concentric magnets includes a region that acts as a non-uniform wide dipole gap. In this region, the magnetic paths of the start and return are generated in the radial direction and travel between opposite poles of the concentric magnets. In effect, the wide gap radial field consists of two effective single poles of opposite polarity that together close the circuit in a flat horizontal plane, thus forming a non-uniform gap. In this region, the opposite poles are focused and the flux density is enhanced through the coils in a relatively tight horizontal pattern, the bipolar gap region of the present invention is relatively wide due to the relatively wide drive coils required. As the size of the dipole gap increases, the flux uniformity therein decreases. The wide gap thus provides a reduction in the uniformity of the magnetic field. This is in contrast to the narrow gap uniform dipole magnetic field of the prior art, which is not of interest for the present invention. Thus, the flat ring coil of the present invention is immersed in a non-uniform magnetic field from either a closed field (double boundary) magnet assembly or an open field (single boundary) magnet assembly. Such a non-uniform magnetic field can also be formed by a number of different magnet configurations as previously described.

A variety of other magnet assembly shapes are also possible. For example, fig. 37 shows a pair of arcuate magnets 120, 120' and a similarly shaped drive coil 52. FIG. 38 shows a plurality of arcuate magnets that are combined to form a generally circular shape. In one arrangement, each arcuate segment is a magnet pair. In another arrangement, the magnet pairs 120, 120' alternate with nonmagnetic arcuate material 130 spaced therebetween. Figures 39, 40 and 41 show perspective views of a square permanent magnet 140, magnet pair 140, 142 and one or more square drive coils 52, 55'. Figures 42, 43 and 44 illustrate the use of rectangular magnets 140, rectangular magnet pairs 140, 142 and one or more rectangular drive coils 52, 52'. In the embodiment of fig. 44, a plurality of non-magnetic materials 150 are disposed between two bar magnet pairs to form a square ring shape. The square outer drive coil 52 is used to encase the entire square and the square inner drive coil 52 is used inside the entire square.

The magnet assembly may be supported by any number of known means. For example, the magnets may be secured to the cover plate and the drive coil coupled to the cover plate via a spring or other compressible material. Furthermore, since the transducer is used in an audio device or a switch or relay, the drive coil may be attached to a component that may be configured to act as a driver, such as a spider, diaphragm, external interface, or flexure (e.g., foam). For example, in figure 45, foam interface member 160 is used to attach the outer periphery of the drive coil to support 170. Such support attachment means are generally applicable to convergent and divergent magnet arrangements. As known to those skilled in the art, various types of support devices may be used. The transducer of the present invention is unique in that it uses a flat ring-shaped drive coil positioned in a radial radiation field. The support device is a second feature and is determined in part by the intended use of the converter.

In addition, physically small transducers can be manufactured using correspondingly small magnet assemblies. Because of the small mass of the small magnet, its inertia is small and the force required for displacement is small. For this reason, the compact transducer formed according to the present invention can be constructed in such a manner as to clamp and fix the drive coil when the magnet assembly is swung; or in addition, both the magnet assembly and the drive coil are allowed to oscillate. Experiments were also successful when both the drive coil and the magnet wire assembly were found to be unclamped and fixed, but the movement was independent of the support device, so the drive coil and magnet assembly were free to interact.

From the foregoing, it can be appreciated that the transducer of the present invention is designed to achieve maximum drive coil excursion while reducing the vertical dimension of the transducer, allowing the overall transducer to be flatter. The converter is axially symmetrical about its longitudinal axis and bilaterally symmetrical about a horizontal plane perpendicular to the vertical axis. With this design, the device can be configured to cover a wide range of frequencies from very low frequencies, to ultra-single waves, and to the radio frequency spectrum.

Symmetry is important to maintain a linear response across a broad frequency spectrum and to keep signal distortion to a minimum. The physical symmetry of the device appearance reflects the magnetic field symmetry absolutely. This represents bilateral magnetic field symmetry above and below the horizontal plane, which helps the signal to more smoothly escape through the drive coil. Many prior art transducers suffer from signal distortion due to lack of symmetry due to the magnet assembly and pole piece architecture. These prior art transducers have axial symmetry without symmetry across the horizontal plane, and the magnet assembly of the transducer of the present invention is symmetric above and below the coil. The coil is positioned on its horizontal surface and bisects the magnet assembly into two halves. One half is above the coil and the other half is below the coil, so the coil is in the center of the magnet system, inside the assembly or around the outside of the assembly. The magnet system center is the location of maximum flux density of the radial magnetic field of a magnet assembly containing two or more axially magnetized magnets, or a magnet assembly having one or more radially magnetized magnets. Such that the horizontal plane represents the strongest part of the magnetic field. This is why the coil is placed in the magnetic region to receive the maximum magnetic field strength from the magnet assembly. This position can also be balanced symmetrically with respect to the field line geometry. The flat ring coil reduces the size and weight of the magnet assembly and greatly improves performance by replacing the cylindrical coil with a radially generated magnetic system.

In contrast to the prior art, the converter of the present invention is a closed loop path device, which in the most practical embodiment of the present invention is a mutually exclusive field isolated path converter. The reason for this is that the device operates with a magnetic field generated radially by the monopole, where the opposite pole does not contribute to the coil. In other words, the opposite poles are not aligned with the plane of the coil, and in order to close the magnetic circuit, the flux lines may bend the return path up to 180 degrees in the opposite direction from where the coil passes and at some separation distance. Previous non-return paths have failed to utilize two poles for coil interaction. The non-return path switch has a coil that interacts with one pole of the magnetic field at a time. The coil does not use both the start and return paths, but rather at different times. The effective unit is the specific region of the non-return path, i.e., the strongest portion. In the non-return path arrangement, the coil is immersed in a uniform bipolar spacing. The coil may perceive the effect of the start path and the return path.

Embodiments of the transducer of the present invention utilize radially generated magnetic fields or magnet segments that appear or generate radial lines. It is important in the present invention that the flat ring coil is immersed in a radial field and that the coil is flat, i.e. the width of the coil is equal to or greater than the height of the coil. The transducer of the present invention is then configured such that the flat ring coil is positioned in a position where the radially generated magnetic field is most effective. The purpose of the radial magnetic field through the flat ring coil is to ensure that all of the windings of the coil are simultaneously immersed in the emanating flux lines. Particularly when the flat wire winding has the broad side of the wire parallel to the longitudinal axis, the greatest number of flux lines can cross the coil winding when the coil is immersed in a radial magnetic field.

The larger the wire contact surface area in a set of closely stacked windings, the larger the increase in existing small capacitance. In flat wide wire or ribbon wire coils, the capacitance increase is considerable. This adds a capacitive reactance component to the coil. As the frequency of the converter increases, the capacitive reactance decreases. The two are inversely proportional. Reactance is the addition of more resistance to the original dc resistance in an ac system. The resistance of the flat wire coil itself decreases as the frequency increases. This makes the coil more efficient. Experiments have shown that the unique properties of the flat ring coil of the present invention can provide performance advantages.

Flat ring coils also offer advantages over multilayer cylindrical coils. The coil itself is flat and the coil is not a solid disk-shaped coil but a ring-shaped coil, and the inductance tends to be lowered, the larger the outer diameter of the coil, the smaller the inductance. Since the continuous winding of the flat ring coil continues to extend the diameter of the coil, the inductance continues to decrease as the number of windings increases. This property helps to maintain the resistance down to a minimum by causing an increase in coil resistance for the additional windings.

Just as frequencies affect capacitive reactance, frequencies also affect inductive reactance. But for inductive reactance, the frequency changes in a linear proportional relationship. This means that the inductive reactance is lowest at low frequencies, which results in higher resistance at high frequencies.

The overall reduction in resistance across the entire coil frequency range caused by the physical construction of the coil, the capacitive reactance and the inductive reactance all contribute to a reduction in coil back electromagnetic force (CEMF) of the electromagnetic system of the converter. CEMF reduction can reduce damping effects, improving device performance by providing more power to the device during operation.

The flat ring shape of the coil, the biaxial symmetry of the magnet assembly, the increased capacitance and the reduced inductance constitute a synergistic effect, producing a more linear and undistorted signal relative to the cylindrical coil and pole piece. Signal filtering no longer requires the addition of electronic components. The additional electronic components contribute to an undesirable degree of phase shift. Phase offsets reduce the output signal strength because destructive wave interference has a canceling effect on the waveform. Thus, the inventive coil is self-tuning and self-filtering over a wide frequency spectrum.

Other advantages of the invention are that heavy and bulky pole pieces can be completely eliminated. The pole pieces are a source of deleterious effects. The pole pieces cause eddy currents, signal rectification, and heat accumulation. The eddy currents formed by induction in the pole piece cause heat build-up inside the pole piece. This heat is transferred to the coil. The additional heat increases the dc resistance of the coil, impeding the flow of current, which in turn generates more heat. This results in a large reduction in output power and a reduction in coil life. The coil overheating may burn out or have a very short life. Another pole piece problem is that the coil is continuously magnetically pulled to the ferrous metal regardless of the coil signal polarity. The result is undesirable signal conditioning and other higher harmonic distortion problems.

Coil overheating may also result from the gap in which it sits being too narrow. As a result of the limited space, heat transfer to the surrounding air becomes difficult. The limited gap area prevents the coil from overheating. Unfortunately, cylindrical coil designs are designed to be left in a very confined and heavily ferrous environment.

In contrast, the flat ring coil of the present invention is placed in open air. Excess heat is dissipated instantaneously. The oscillation of the coil allows the coil itself to fan out continuously during operation. Yet another additional benefit to cooling is that because the coil is flat, most or all of the wire is in direct contact with the air. There are no heavy layers of windings that prevent the inner layer from contacting the outer layer. Wires buried deep inside the coil have little chance to transfer heat, especially when the surrounding windings are all hot, deep windings have little chance to transfer heat. The coil of the invention can easily dissipate heat, so that the coil can absorb larger wattage. The larger diameter of the ring also allows it to absorb additional power.

The flat ring coil radiates a magnetic field in a radial direction, providing higher performance than the cylindrical coil without loss and signal distortion, and reducing weight by many times. Weight versus power output experiments show that the transducers of the present invention are several times more powerful than known pole piece transducers (rated in root mean square power). The converter of the present invention does not suffer from magnetomotive force or electromotive force losses associated with other prior art converters.

The transducer of the present invention also provides a number of magneto-mechanical advantages. The length of the cylindrical coil of several prior art ferrous pole piece converters prevents all of the windings of the cylindrical coil from being placed in the magnetic field simultaneously as the coil moves up and down the narrow uniform dipole gap established by the pole pieces of the magnet assembly. At some point the top and/or bottom ends of the cylindrical coil extend beyond the magnetic field, and often many coils extend beyond the pole piece edge wire or corner during reversal of direction when approaching an excursion boundary. This results in an uneven distribution of magnetic flux density along the coil axis, which is a common source of signal distortion. The fringe fields present at the edges or corners of the pole pieces also cause distortion amplification due to the fringe field lines being non-orthogonal to the longitudinal axis of the cylindrical coil (since they are typically tied within the narrow pole piece gap) and instead forming angles that deviate from orthogonal. As the coil approaches the magnetic field, the coil modulates the side band field, causing the signal to be more distorted. The problems caused by the cylindrical coil are further exacerbated by the radially generated magnetic field.

In a radial system, the flat ring coil of the present invention is short in height so that substantially all of the windings are in the field density region where the flux lines pass through the coil at substantially equal angles simultaneously as the field density region progresses around the periphery of the magnet assembly. This was not the case with previous cylinder coils, however, where flux lines at different angles may contact the windings at any given instant. Although the flux density decreases as the distance of the magnetic monopole increases through successive windings of the radial system flat ring coil, the flux line angle through the coil remains nearly equal. Conversely, the columnar coils have different angles of flux lines through their winding lengths.

As a result, the flat ring coil does not have coils that are subject to magnetic field conditions having flux lines at different angles at a time. This avoids the problem of the coil encountering flux lines of different angles, which ultimately results in the magnetic field being neutralized to zero at some point during coil excursion, as would be encountered with prior art cylindrical coils. In other words, because the flat ring drive coil extends only a small amount along the longitudinal axis, the flat ring coil does not experience the "cross fire" of the magnetic field regions at different angles, thereby causing destructive interference. A flat ring coil can pass through zero field density without conflicting magnetic field lines. For this reason, the flat ring coil is rarely distorted over its travel distance. There is no problem of magnetic field neutralization during operation of the drive coil due to destructive interference of the colliding flux lines. The waveform remains clear and the response of the coil is more linear.

Because the windings of the flat ring coil receive flux lines at the same angle at any given time, the problem of unwanted side-band field modulation does not occur as if the cylindrical coil were placed in a radial magnet system. The advantage of a flat ring coil is that it extends only a small amount in the longitudinal axis. This side band phenomenon, which is detrimental to the cylindrical coil, becomes advantageous for the operation of the flat ring coil. The sideband effect of the radial magnetic field can also be created by axially oriented magnets, which can be achieved for the transducer system of the present invention whether the magnet assembly consists of only a single magnet or a stack of several magnets.

As the flux lines fan radially outward from the magnetic monopole, weakening of the magnetic field is felt at each successive winding of the flat ring coil, but the magnetic field remains at the same angle throughout the circumference and windings of the coil at a given instant. The flat ring coil exhibits a quantitative change in magnetic flux density at a given instant, but no qualitative change in magnetic flux density. The term "qualitative" refers to the angle at which the lines of magnetic flux pass through the drive coil. The term "quantitative" means that for lines of magnetic flux having a given angle, the degree of magnetic flux density or magnetic field strength changes with increasing distance from the source. The winding of the columnar coil generates qualitative and quantitative changes in magnetic flux density at a given time. The flat ring coil is subjected only to quantitative magnetic field changes. Thus, the qualitative parameters affecting the coil are removed, and the signal distortion source that the cylindrical coil cannot prevent is removed.

The flat ring coil therefore reacts more uniformly to fluctuations in the surrounding magnetic field. In contrast, the cylindrical coil has a non-uniform response to fluctuations in the magnetic field in the surrounding environment due to the physical extension in the longitudinal axis direction, and the cylindrical coil is simultaneously affected by the magnetic field lines of different angles. This non-uniform response to the magnetic field of the cylindrical coil causes additional fluctuations in the B1i vector cross-product from the qualitative parameter, where B is the magnetic flux through the coil, 1 is the magnetic field wire length and i is the wire current, causing additional distortion of the signal. Such disadvantageous parameters are not readily apparent in the flat ring coil of the present invention, so that the present invention provides a clearer and purer signal.

The transducer of the present invention also provides an advantageous excursion path for its flat ring drive coil, and in particular the present invention avoids uncontrolled excursions. In the transducer of the present invention, the permanent magnet return path does not contribute to coil activity at the same time as the start path. The return pole is too far from the coil to have a direct effect on the coil and requires a travel time to reach the vicinity of the coil. The field lines of the return path are not in the same radial or horizontal plane of the start path. The effective monopole or "radiation field" of the starting path is located at the center of the assembly (for an axial pair magnet assembly or a radial magnet assembly). Here the coil can take advantage of the B1i cross product if both the start and return paths are collinear, such as a uniform dipole field gap between ferrous pole pieces. The narrow dipole gap of conventional cylindrical coils is maintained during excursion, both in the start and return paths.

In either the axial magnet pair or radial magnet arrangement, the drive coil continues to advance along its longitudinal axis away from the radial field at the center of the assembly toward the extreme ends of the magnet assembly. As the coil advances, it encounters another radial field, but of opposite polarity. This field represents the return path of the magnetic circuit, originating from the polar end faces of the magnet system, on opposite sides of the middle of the assembly. The end magnetic field acts on the coil, braking the coil speed, holding the coil by magnetic attraction until the polarity of the coil current is reversed. The coil is then advanced in the opposite direction toward the center of the assembly. Continuing to reach the other end field at the opposite end (if there is sufficient momentum), or the coil returning to the radial field in the opposite polarity middle region, then returning to the end pole where the end field again brakes the momentum of the coil, and the cycle begins anew. Braking of the coil helps prevent damage due to excessive excursion, i.e., excessive extension beyond the excursion boundary, from causing runaway.

In either the axial magnet pair or radial magnet pair arrangement, the flat ring coil typically does not travel beyond the plane of the open pole piece at the end of the assembly. Conversely, if the cylinder coil is placed in the non-return path magnet assembly, the cylinder coil will brake half or more beyond the pole faces. The cylinder coil is not easily stopped because the cylinder coil is offset by the magnetic field caused by the magnetic field lines at various angles. The cylindrical coil has a greater risk of being flushed out of the magnet assembly, thereby causing an uncontrollable runaway phenomenon. In the invention, the flat annular coil does not exceed the assembly, but can be maintained on the end face of the magnetic pole by magnetic force. And then reverse direction when the polarity of the power is changed.

Since the flat ring coil has only a small physical extension of the longitudinal axis, the strong magnetic field holding the coil will not be weakened by magnetic field lines of opposite polarity and different angles, as in the case of a cylinder coil. Thus, the qualitative parameters relating to the angle of the magnetic field collision can be largely eliminated, since the flat ring coil is short in longitudinal extension.

The braking of the flat ring coil helps to eliminate physical constraints on the coil, thereby resulting in limiting its movement within the confines of the excursion boundaries. Runaway excursion is particularly prevalent at low frequencies where the excursion path is at a maximum. The transducer of the present invention can avoid the main cause of such coil damage by magnetic force without using physical means to cause excessive damping. The output of power is not impaired. In some embodiments of the invention, the "magnetic cord" eliminates the need for interface material to secure the drive coil to the magnet assembly.

The flat ring coil has the aforementioned advantages over the cylindrical coil in either the non-return system or in the more popular radial system, thus making the transducer of the present invention most satisfactory for use in a variety of different applications as a novel technique.

In other words, the device of the present invention is designed to maximize coil excursion while reducing the longitudinal dimension of the transducer to make it flatter overall. Axially symmetrical about its longitudinal axis, and bilaterally symmetrical about a horizontal plane perpendicular to the longitudinal axis. Such devices can be configured to cover a wide frequency range, from very low frequencies, through ultrasound, to the radio frequency spectrum. Symmetry is important to maintain linearity of response over a wide frequency spectrum range and to maintain minimization of signal distortion. The symmetry of the magnetic fields at the upper and lower sides of the horizontal plane helps to make the signal smoother when the coil is in excursion. The flat ring coil reduces the size and weight of the magnet assembly and replaces the cylindrical coil of a radial magnet system, resulting in greatly increased performance. Flux lines having the same angle pass through the flat ring coil, but the cylindrical coil is common to flux lines having different and opposite angles and thus the interference parameter in the cylindrical coil increases.

The transducer of the present invention is particularly useful for a speaker 196 and a microphone 198. Fig. 46-54 show various speaker embodiments. In general, bilateral symmetry (electrical, magnetic and mechanical) helps to improve speaker performance, and preferably includes such symmetry for each component. Fig. 55-64 show various microphone embodiments. In speakers and microphones, the assembly includes a diaphragm that emits or receives sound based on the relative movement of the coil and magnet system. It will be appreciated from a study of the following description that the arrangement of speakers and microphones may be varied depending on the particular application, and that a variety of features may be used in accordance with the foregoing description.

Referring first to the embodiment of fig. 46, the speaker includes a magnet assembly 50, a conductor 52 (drive coil), a diaphragm 200, a support 202 (or base), and a collar 204. The magnet assembly and coil are arranged as described previously so that the coil is immersed in the laterally emanating magnetic field. As explained above, a space s is left between the coil and the magnet assembly, so that there is more relative movement between them without collision. This space is preferably as small as technically feasible.

The support serves to stabilize the loudspeaker. In fig. 46, the support 202 includes a brace 206 and an enclosure 208. The stay bar is connected to the magnet assembly and the enclosure. The enclosure is a flat stiffened panel within which other components are secured. The brace includes one or more legs 210 that maintain the magnet assembly in position relative to the diaphragm and coil. Fig. 46 shows a single brace, but there may be upper and lower braces sandwiching the perimeter. See, for example, the enclosure of fig. 57.

The diaphragm is an annular member, preferably made of a hard and light material. The stiffness of the diaphragm may be increased by adding ribs or concentric circles 212. The coil is attached to the diaphragm at a location proximate the magnet assembly. Refer to fig. 66.

An annular collar 204 is attached to the enclosure around the outer periphery of the diaphragm. The collar is typically a flexible member that connects the diaphragm to the enclosure, thereby allowing relative movement of the diaphragm within the enclosure. In one embodiment, the outer periphery of the diaphragm is adhered to the inner periphery of the collar. The collar of figure 46 is shown as a foam ring having a rectangular cross-section. In FIG. 47, the collar is a ring of flexible material in the shape of a transverse spring. In fig. 48, the collar is a dome-shaped annular ring. Figure 49 shows a double dome configuration. Alternatively, a collar such as an accordion type collar may be used, as described in U.S. Pat. No. 3,019,849 (incorporated herein by reference). During use, the collar allows the entire diaphragm to translate during the excursion path without only the portion of the diaphragm closest to the coil.

Other embodiments of speakers are shown in fig. 50 and 51. In these configurations both the coil and the magnet assembly move. One or more cross-shafts 214 connect the magnet assembly to the diaphragm. For lower frequencies, the cross-bar helps to physically control the diaphragm and coil. In FIG. 50, upper and lower ring spiders are used to connect the inner edge of the diaphragm to the magnet assembly. A soft iron ring 216 may be placed between the magnets to assist in focusing the magnetic field lines. Similarly, iron or copper disks 218 may be attached to the top or bottom of the disk pair. Alternatively, a disk of bismuth may be used to magnetically shield the magnet assembly above or below it. In fig. 51, the diaphragm is made of a compressible material. The inner periphery of the diaphragm compresses and becomes stiffer. The coil is attached to this stiffener 222.

Fig. 52 is a schematic plan view of an exemplary embodiment of a loudspeaker, showing a support 202 formed as a combination of an enclosure and a brace. The support rod supports the magnet assembly, the enclosure supports the collar and the diaphragm. The strut is shown with three arms 224 extending from a midpoint 226. The magnet assembly is fixed to the midpoint and the distal end of the arm includes a foot 210, the foot 210 being attached to the enclosure just outside the collar region.

The present transducer can also be used with known speakers as replacement components. For example, refer to fig. 53, wherein a speaker assembly is provided with the transducer of the present invention in place of a conventional magnet assembly and cylindrical coil. Figure 53 is further modified to include two back-to-back speaker assemblies. In this embodiment, speaker cone 228 is attached to former 230. The cone and form translate in and out and are supported by cross 214. The forming member moves telescopically on the magnet assembly. A toroidal coil 52 is attached to the outer surface of the form at the location where the magnetic field is emitted from magnet assembly 50. The magnet assembly is attached to the basket 232, preferably with an optional ferrous disk 216 interposed therebetween, the disk 216 being attached to the basket.

The speaker of fig. 53 may also be arranged so that the magnet assembly is movable and the coil is stationary. In this configuration, the former is connected to the magnet assembly. The magnet assembly is disengaged from the basket. The coil is supported against the basket side walls by struts.

Regardless of the configuration, in either cone or diaphragm systems, or single or dual axis magnet assemblies, care is taken to ensure that the design avoids any sound cancellation effects.

Similarly, multiple diaphragms may be arranged in a vertical position. For example, referring to the embodiment of fig. 54, where the speaker is configured to produce sound in two opposite directions using two different diaphragms 200. The magnet assembly may be a bipolar magnet assembly disposed with opposite ends in contact. Figure 53 generally illustrates the application of this embodiment to a conventional loudspeaker conical diaphragm. This arrangement has a mild steel spacer (or other material) between the opposed pole magnet pairs. The magnet assembly may be two bipolar magnet assemblies with an optional spacer magnet in between (e.g., as shown in fig. 54). Alternatively, the magnet assembly may comprise two single pole systems with a spacer magnet in between. In various embodiments, the support preferably includes non-magnetic elements 234 of the support at locations between the membranes to reduce interference.

Referring now to microphones, many known microphones are simply scaled down versions of conventional speakers, and operate in reverse (i.e., as generators). Referring to fig. 55, a first embodiment of a microphone is shown housed in an upper and lower circular support 202. The support body delimits an inner space in which the system is housed. In the illustrated embodiment, the magnet assembly is attached to the inner surface of the support. The diaphragm 200 is sandwiched between supports and includes an inner opening with an inner periphery. The coil 52 is attached to the diaphragm proximate this opening. (As previously discussed, the coil may be attached to the diaphragm in a variety of ways at a variety of different locations). After assembly, the coil is positioned close to the magnet assembly but not touching. The diaphragm 200 is typically made of a lightweight stiff material that can accommodate oscillation while still providing sufficient support for the coil. If desired, the diaphragm may include concentric ribs or other reinforcing shaped structures 212. These structural elements provide stiffening of the diaphragm body while also providing a collar function at the outer periphery of the diaphragm to increase the excursion path. In this regard, the collar may be established to the septum. The collar is an optional element, since the diaphragm of the microphone oscillates very weakly, and the coil does not need a large excursion path to function.

Figure 56 shows another embodiment of a microphone formed in accordance with the present invention. In the present device, the support body includes upper and lower circular elements 236. The magnet assembly includes a pair of axially magnetized ring magnets positioned axially and sandwiched between upper and lower members 236. Each element includes an inner support arm 238 extending inwardly from the inner surface of the element. The diaphragm is shaped as a circle with a middle portion 240 that is thicker than the rest of the diaphragm. The thicker middle portion is fixedly secured between the inner support arms of the upper and lower members. The coil is attached to the diaphragm around its outer periphery and is proximate to the ring magnet assembly. An optional built-in collar or rib (not shown) may be used to nest the middle portion to assist in diaphragm oscillation.

In fig. 55 or 56, additional magnet elements may be used to assist in focusing the magnetic field. For example, fig. 55 and 56, the support is made of a magnetic material. In addition, ferrous discs may be used within the magnet assembly itself. Refer to fig. 57.

Another microphone configuration is shown in fig. 58, in which the coil 52 is held stationary, allowing the magnet assembly 50 to move relative to the coil. In this case, the diaphragm 200 is attached to the magnet assembly in the form of two opposing circular cloths 242 that encase the magnet assembly. The coil 52 is held on the stiffening support 244. The ends of the support and the ends of the diaphragm are clamped between two support rings 246.

The supports of fig. 55, 56 and 57 include openings to allow sound to travel through either side of the microphone and move the diaphragm. In this way this arrangement can be made bi-directional or referred to as "bipolar", which can respond to sound from either side. Fig. 62, 63 and 64 show various configurations of such enclosures.

FIGS. 59, 60 and 61 show other embodiments of microphones made in accordance with the present invention. In this configuration, the magnet assembly consists of a single axis magnet attached to the lower magnetic support 202. This arrangement is therefore referred to herein as a "monopole" system, with only a single pole face producing the majority of the magnetic field. Furthermore, such systems are typically only responsive to sound from a single direction.

The lower support includes inwardly oriented circular side flanges 247. The support is a single article made of a magnetic material. The magnetic poles at the distal ends of the flanges have opposite extremes at the upper surfaces of the magnetic poles of the magnets. Because of the overall weakness of the magnet assembly, such arrangements include a ferrous disc attached to the upper pole face to focus the magnetic field. This arrangement also includes a collar interposed between the flange and the diaphragm to facilitate movement of the diaphragm. Also suitable for use in the present invention are ferrous fluids (iron maintained in suspension).

The collar 204 may be of many different types. The collar of fig. 59 is a foam ring. In addition, concentric ribs on the outer periphery of the diaphragm may serve as suspension attachments. Such as fig. 66. The collar of fig. 60 is a gel ring or a gel foam ring. The collar of fig. 61 is a rubber ring with a U-shaped slot.

One or more moving coils 52 are attached to the diaphragm 200 in a position immersed in the magnetic field. In fig. 59 and 60, near the outer pole face of the central single magnet. Figure 61 shows a second coil located at the outer periphery of the diaphragm, near the polar material of the support flange. A lead wire enters the inner coil and then is connected to the outer coil, supplying a second lead wire.

Fig. 60 and 61 show the optional dome 248 positioned over the central single magnet. The dome increases the surface of the incoming sound and is directly attached to the diaphragm. The dome is preferably made of the same stiff material as the diaphragm and may be manufactured separately from the diaphragm or integrally therewith (as shown in figure 61). As can be appreciated from a review of the foregoing, unipolar designs may be combined to form a bipolar configuration. No dome is required in this combination.

Different novel and useful designs may be created by combining the teachings described herein. For example, a speaker with a push-to-talk (PTT) switch known in the art may be modified using the arrangement of fig. 65 or 66. In FIG. 65, a dipole magnet assembly having a central ferrous disk is secured within upper and lower magnetic supports. The collar is used to support the annular diaphragm. The inner coil is coupled to the diaphragm inner periphery. An outer coil is attached to the outer periphery of the diaphragm. The inner coil is used for the microphone function; the outer coil is used for the speaker function. The magnetic support arrangement of fig. 66 is similar to that of fig. 65. Figure 66, however, does not have a collar and the outer periphery of the diaphragm includes a series of concentric ribs which serve as the collar. The speaker coil is located on one side of the diaphragm and the microphone coil is located on the opposite side of the diaphragm. In this configuration, the speaker coil and the microphone coil have their own appropriate impedances. A single pole magnet system can also be used for such a device.

In another embodiment, conventional speakers such as tweeters and woofers can be combined into a single speaker without losing their special function, since today separate coils can be used for different purposes, all in a single magnet assembly. In one embodiment, the speaker is formed with a central magnet system surrounded by concentric ring magnet assemblies. Various diaphragms and coils are placed in the emanating magnetic field. Such a configuration may be used to assign different frequencies to different coils. The use of coil and diaphragm dimensions that match the push frequency can be effective.

While the preferred embodiments of the invention have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention. As will be appreciated from a reading of the foregoing, many different configurations can be made using a combination of the numerous elements described herein, such as a combination of axial magnets (disk, ring, or other shape), interface members, spacers, end caps, open spaces, radial magnets, magnet pairs, cross-shafts, supports, collars, various drive coil designs, and the like. Although only some combinations are shown and described herein, this description is not intended to be construed as limiting. In addition, the various elements described herein may be a single item or composed of multiple components.

Claims

1. An electromagnetic converter, comprising:

(a) a magnet assembly comprising at least one magnet, the at least one magnet having an axial magnetization; the magnet assembly including first and second opposed outer pole faces and a magnetic field radiating radially outwardly transverse to the axial magnetization direction; and

(b) a conductive drive coil having an outer dimension and an inner dimension; the coil has a height dimension and a width dimension, the width dimension being defined as the spacing between the inner dimension and the outer dimension of the coil; the width dimension of the drive coil is at least equal to the height dimension; the drive coil is positioned in the radially emanating magnetic field of the magnet assembly; a space exists between the at least one magnet and the drive coil such that, during use, the drive coil is not in physical contact with the at least one magnet; the drive coil moves along an excursion path, at least part of which is located between the first and second outer magnetic pole faces;

wherein, after assembly, the drive coil is mounted adjacent the magnet assembly such that relative axial movement can occur between the drive coil and the magnet assembly during use; wherein during use as a motor, current is supplied to the coil causing the coil and magnet to move relative to each other; and during operation as a generator, external physical movement of the drive coil relative to the magnet causes a corresponding current to be generated in the drive coil.

2. The transducer according to claim 1, wherein the magnet assembly comprises a single axial magnet having opposing first and second pole faces; the single magnet has a magnetic field that radiates radially outward from each pole face; the drive coil of the magnet assembly is located at one of the magnet pole faces within the outwardly emanating magnetic field thereof.

3. The transducer according to claim 2, wherein the single magnet is a disc magnet; the disc magnet includes an outer diameter dimension; the inner dimension of the driving coil is the inner diameter dimension, and the outer dimension of the driving coil is the outer diameter dimension; and wherein the drive coil inner diameter dimension is greater than the disc magnet outer diameter dimension.

4. The transducer according to claim 2, wherein the single magnet is a ring magnet having a radially inwardly radiating magnetic field and a radially outwardly radiating magnetic field; the conductive drive coil is positioned in one of the inwardly emanating magnetic field and the outwardly emanating magnetic field.

5. The transducer according to claim 4, wherein the ring magnet includes an outer diameter dimension; the drive coil inner dimension is an inner diameter dimension and the drive coil outer dimension is an outer diameter dimension; the drive coil has an outer diameter dimension that is less than an inner diameter dimension of the ring magnet such that the drive coil is positioned inside the ring magnet during use.

6. The transducer according to claim 1, wherein the magnet assembly comprises first and second axial magnets; the magnets are coaxially arranged, and the same magnetic pole faces face each other, so that a radial radiation magnetic field is formed from the area where the magnetic pole faces face each other; the drive coil is located in this magnetic field.

7. The transducer according to claim 6, wherein the first and second axial magnets are disc magnets; the disc magnets each include an outer diameter dimension; the inner dimension of the driving coil is the inner diameter dimension, and the outer dimension of the driving coil is the outer diameter dimension; and wherein the drive coil inner diameter dimension is greater than the disc magnet outer diameter dimension.

8. The transducer according to claim 6, wherein the first and second axial magnets are ring magnets arranged with like poles facing each other, thereby forming a radially inwardly radiating magnetic field and a radially outwardly radiating magnetic field; the conductive drive coil is positioned in one of the inwardly emanating magnetic field and the outwardly emanating magnetic field.

9. The transducer according to claim 8, wherein the ring magnet includes an outer diameter dimension; the drive coil inner dimension is an inner diameter dimension and the drive coil outer dimension is an outer diameter dimension; the drive coil has an outer diameter dimension that is less than an inner diameter dimension of the ring magnet such that the drive coil is positioned inside the ring magnet during use.

10. The transducer according to claim 1, wherein the magnet assembly comprises at least one arcuate magnet.

11. The transducer according to claim 1, wherein the magnet assembly comprises at least one rectangular magnet.

12. The transducer according to claim 6, 7, 8 or 9, wherein the magnet assembly further comprises a first interface member located between the first and second magnets and coupled to the drive coil.

13. The transducer according to claim 12, wherein the first and second magnets are directly attached to opposite sides of the first interface member.

14. The transducer according to claim 13, wherein the first and second magnets are directly attached to opposing sides of the first interface member using an adhesive.

15. The transducer according to claim 1, 2, 3, 4, 6, 7, or 8, wherein the drive coil has a width dimension that is greater than a height dimension of the drive coil.

16. The transducer according to claim 1, wherein the drive coil comprises a spirally wound flat wire of a conductive material, the flat wire being wound in an upright orientation.

17. The transducer according to claim 16, wherein the height of the flat wire is at least as great as three times its thickness.

18. The transducer according to claim 16, wherein the drive coil includes a helically wound ribbon wire of conductive material, the ribbon wire being wound in an upright orientation.

19. The transducer according to claim 1, wherein the drive coil is made of a wire having a rectangular cross-sectional shape.

20. The transducer according to claim 6, wherein the magnet assembly further comprises a spacer positioned between the first magnet and the second magnet.

21. The converter of claim 20, wherein the spacer is made of a ferrous material.

22. The transducer according to claim 20, wherein the spacer is in the shape of a disc.

23. The transducer according to claim 22, wherein the diameter of the spacer and the outer dimensions of the first and second magnets are equal.

24. The transducer according to claim 1, 2 or 6, wherein the magnet assembly further comprises first and second end caps, one end cap being located above the first outer pole face and the other end cap being located below the second outer pole face.

25. The converter of claim 24 wherein the end caps are made of a ferrous material.

26. The transducer according to claim 1, 2, or 6, wherein a space between the drive coil and the magnet assembly is in a range of about 0.5 mm to about 5 mm.

27. The transducer according to claim 1, 2 or 6, wherein the magnets of the magnet assembly remain stationary and the drive coil is made movable relative to the magnets.

28. The transducer according to claim 1, 2 or 6, wherein the drive coil is held stationary while the magnets of the magnet assembly are movable relative to the drive coil.

29. The transducer according to claim 1, 2 or 6, further comprising a holding device for holding the magnet assembly stationary and allowing the drive coil to move relative to the magnet assembly.

30. The transducer according to claim 1, 2 or 6, further comprising a support strut and flexible interface members attached to the support strut and to the drive coil.

31. The transducer according to claim 30, wherein the flexible interface member is made of foam.

32. An electromagnetic converter, comprising:

(a) a magnet assembly including first and second disc magnets having axial magnetization; the magnets are coaxially arranged, and the same magnetic pole faces are opposite to each other; the magnet assembly thus forming a magnetic field that radiates radially outwardly across the axial magnetization direction; the magnet has a maximum outer diameter dimension at a position where the transverse magnetic field is radiated outward; and

(b) a conductive drive coil having an outer diameter dimension and an inner diameter dimension, the inner diameter dimension of the drive coil being greater than the largest outer diameter dimension of the first and second magnets; the conductive drive coil being located outside the first and second disc magnets and within the outwardly emanating transverse magnetic field; a space exists between the magnets and the drive coil such that, during use, the drive coil does not physically contact the magnets; the coil has a height dimension and a width dimension, the width dimension being defined as a distance between an inner diameter dimension and an outer diameter dimension of the coil, the width dimension being at least equal to the height dimension;

wherein when assembled, the drive coil is mounted adjacent the magnet assembly such that relative axial movement can occur between the drive coil and the magnet assembly during use.

33. An electromagnetic converter, comprising:

(a) a magnet assembly having first and second ring magnets with axial magnetization; the annular magnets are coaxially arranged, and the same magnetic pole surfaces are opposite to each other; whereby the magnet assembly forms a radially inwardly emanating magnetic field and a radially outwardly emanating magnetic field; the ring magnet having a minimum diameter dimension at a location where the magnetic field is radiated inwardly; the ring magnet having a maximum outer diameter dimension at a location where the magnetic field is radiated outward;

(b) a conductive drive coil having an outer diameter dimension and an inner diameter dimension, the conductive drive coil being positioned in one of the inwardly emanating transverse magnetic field and the outwardly emanating transverse magnetic field; a space exists between the ring magnet and the drive coil such that during use the drive coil does not physically contact the magnet; the coil has a height dimension and a width dimension, the width dimension being defined as a distance between an inner diameter dimension and an outer diameter dimension of the coil, the width dimension being at least equal to the height dimension; and

34. The electromagnetic transducer of claim 33, wherein the drive coil is positioned within an inwardly emanating magnetic field of the first and second ring magnets.

35. The electromagnetic transducer according to claim 34, further comprising a second conductive drive coil positioned in the outwardly emanating magnetic field of the first and second ring magnets.

36. An electromagnetic converter, comprising:

(a) a magnet assembly including at least one ring magnet having radial magnetization; the magnet assembly includes first and second opposing outer surfaces, an outer diameter surface and an inner diameter surface; the magnet assembly further includes a magnetic field radiating radially outward from the outer diameter surface in a direction parallel to the outer surface of the magnet and returning inward at the inner diameter surface of the magnet; the ring magnet having a minimum diameter dimension at the location of the return magnetic field; the magnet assembly having a maximum outer diameter dimension at a location where the magnetic field is emitted outwardly;

(b) a conductive drive coil having an outer diameter dimension and an inner diameter dimension, the conductive coil being positioned in one of the return magnetic field and the outwardly emanating magnetic field; a space exists between the ring magnet and the drive coil such that during use the drive coil does not physically contact the magnet; the coil has a height dimension and a width dimension, the width dimension being defined as a distance between an inner diameter dimension and an outer diameter dimension of the coil, the width dimension being at least equal to the height dimension; and

37. The electromagnetic transducer of claim 36, wherein the drive coil is located within an outwardly radiating magnetic field.

38. A method of manufacturing a transducer comprising:

(a) forming a magnet assembly having at least one magnet with axial magnetization; the magnet assembly further includes first and second opposed outer pole faces and a magnetic field radiating radially outward in a direction transverse to the axial magnetization;

(b) providing a conductive drive coil having an outer dimension and an inner dimension; the coil has a height dimension and a width dimension, the width dimension being defined as a distance between an inner dimension and an outer dimension of the coil; the width dimension is at least equal to the height dimension; the drive coil being located within the radially emanating magnetic field of the magnet assembly; a space exists between the at least one magnet and the drive coil such that, during use, the drive coil does not have physical contact with the at least one magnet; and

(c) mounting the drive coil adjacent the magnet assembly such that relative axial movement can occur between the drive coil and the magnet assembly during use; wherein the relative axial movement occurs along an excursion path, at least a portion of the excursion path being located between the first and second outer pole faces of the magnet.

39. A transducer manufactured according to the method of claim 38.

40. A loudspeaker, comprising:

(a) a magnet assembly comprising at least one magnet having an axial magnetization; the magnet assembly including first and second opposed outer pole faces and a magnetic field radiating radially outwardly in a direction transverse to the axial magnetization; and

(b) a conductive drive coil having an outer dimension and an inner dimension; the coil has a height dimension and a width dimension, the width dimension being defined as the spacing between the inner dimension and the outer dimension of the coil; the width dimension of the drive coil is at least equal to the height dimension; the drive coil is positioned in a radial magnetic field of the magnet assembly; a space exists between the at least one magnet and the drive coil such that, during use, the drive coil is not in physical contact with the at least one magnet; the drive coil moves along an excursion path, at least part of which is located between the first and second outer magnetic pole faces; and

(c) a diaphragm coupled to one of the magnet assembly and the drive coil;

wherein, when assembled, the drive coil is mounted adjacent the magnet assembly such that relative axial movement can occur between the drive coil and the magnet assembly during use; and wherein current flow to the drive coil causes relative movement between the magnet assembly and the drive coil, which relative movement further causes physical movement of the diaphragm and thus the generation of sound.

41. The loudspeaker of claim 40, wherein the magnet assembly comprises first and second disc magnets each having an axial magnetization; the magnets are coaxially arranged, with the same pole faces facing each other; the magnet has a maximum outer diameter dimension at the location of the outwardly radiating transverse magnetic field; and

wherein the inner dimension of the conductive drive coil is an inner diameter dimension and the outer dimension of the conductive drive coil is an outer diameter dimension, the inner diameter dimension of the drive coil being greater than the largest outer diameter dimension of the first and second magnets; wherein the width dimension of the coil is defined as the distance between the inner diameter dimension and the outer diameter dimension of the coil.

42. A loudspeaker, comprising:

(c) a diaphragm coupled to one of the magnet assembly and the drive coil;

wherein, when assembled, the drive coil is mounted adjacent the magnet assembly such that, during use, relative axial movement can occur between the drive coil and the magnet assembly; and wherein current flow to the drive coil causes relative movement between the magnet assembly and the drive coil, which relative movement further causes physical movement of the diaphragm and thus the generation of sound.

43. A method of manufacturing a loudspeaker, comprising:

(b) providing a conductive drive coil having an outer dimension and an inner dimension; the coil has a height dimension and a width dimension, the width dimension is defined as the distance between the inner dimension and the outer dimension of the coil; the width dimension is at least equal to the height dimension; the drive coil being located within the radially emanating magnetic field of the magnet assembly; a space exists between the at least one magnet and the drive coil such that, during use, the drive coil does not physically contact the at least one magnet;

(c) mounting the drive coil adjacent the magnet assembly such that, during use, relative axial movement can occur between the drive coil and the magnet assembly; wherein the relative axial movement occurs along an excursion path, at least a portion of the excursion path being located between the first and second outer pole faces of the magnet; and

a diaphragm is disposed and one of the drive coil and the magnet assembly is attached to the diaphragm.

44. A loudspeaker made according to the method of claim 43.

45. A microphone, comprising:

(c) a diaphragm coupled to one of the magnet assembly and the drive coil;

wherein when assembled, the drive coil is mounted adjacent the magnet assembly such that relative axial movement can occur between the drive coil and the magnet assembly during use; and wherein sound causes physical movement of the diaphragm and one of the magnet assembly and the drive coil, whereby relative movement between the magnet assembly and the drive coil further causes a corresponding current to be generated in the drive coil.

46. The microphone of claim 45, wherein the magnet assembly comprises first and second disc magnets, each of the first and second disc magnets having an axial magnetization; the magnets are coaxially arranged, with the same pole faces facing each other; the magnet has a maximum outer diameter dimension at a location where the transverse magnetic field is radiated outward; and

47. A microphone, comprising:

(a) a magnet assembly having first and second ring magnets, the ring magnets having axial magnetization; the annular magnets are coaxially arranged, and the same magnetic pole surfaces are opposite to each other; whereby the magnet assembly forms a radially inwardly emanating magnetic field and a radially outwardly emanating magnetic field; the ring magnet having a minimum diameter dimension at a location where the magnetic field is radiated inwardly; the ring magnet having a maximum outer diameter dimension at a location where the magnetic field is radiated outward;

(b) a conductive drive coil having an outer diameter dimension and an inner diameter dimension, the conductive drive coil being positioned in one of the inwardly emanating transverse magnetic field and the outwardly emanating transverse magnetic field; a space exists between the ring magnet and the drive coil so that the drive coil does not physically contact the magnet during use; the coil has a height dimension and a width dimension, the width dimension being defined as a distance between an inner diameter dimension and an outer diameter dimension of the coil, the width dimension being at least equal to the height dimension; and

(c) a diaphragm coupled to one of the magnet assembly and the drive coil;

48. A method of manufacturing a microphone, comprising:

49. A microphone made in accordance with the method of claim 48.